1. Field of the invention
The present invention relates to a focus retaining mechanism, and more particularly, to a focus retaining mechanism of a camera.
2. Description of the Prior Art
Please refer to FIG. 1. FIG. 1 is a top view of a lens driving device 10 of a camera according to the prior art. The lens driving device 10 is disclosed in U.S. Pat. No. 5,680,649 xe2x80x9cLENS DRIVING DEVICE FOR AUTO-FOCUS CAMERAxe2x80x9d. The lens driving device 10 comprises a base 12 having a cylindrical and vertical opening 16, a focusing lens 14 rotatably fixed within the opening 16, a driving ring 40 rotatably fixed on the periphery of the opening 16 of the base 12, a shutter-driving ring 44 fixed on the base 12 by hooking the driving ring 40, a retaining member 42, a lens barrel 18 mounted on the base 12 by hooking the driving ring 40 and the retaining member 42, a first bi-directional driving motor 20 and a second bi-directional driving motor 30 fixed on the base 12, an elastic element 34 mounted on the base 12, and an electromagnetic valve 22 disposed on the base 12.
In addition, a cylindrical projection 46 disposed on the driving ring 40 engages with an engaging portion 19 of the lens barrel 18. Thus, when the driving ring 40 is rotated, the lens barrel 18 and the focusing lens 14 are also rotated. The second bi-directional driving motor 30 is used to rotate the shutter-driving ring 44 for controlling a shutter. The first bi-directional driving motor 20 is used to drive the electromagnetic valve 22 for mounting the retaining member 42 in a predetermined position so as to rotate the focusing lens 14 to a corresponding position. Moreover, an idler gear 70 and a first ratchet 50 are used for the transmission between the retaining member 42 and the electromagnetic valve 22.
As shown in FIG. 1, when the second bi-directional driving motor 30 rotates the a shutter-driving ring 44 toward a positive direction via a second ratchet 32 to control an opening position of the shutter, the shutter-driving ring 44 pushes the driving ring 40 to rotate the lens barrel 18 and focusing lens 14. At the same time, the driving ring 40 also moves the retaining member 42 so that a plurality of gear portions 43 engages with a hold lever 60 one by one. The retaining member 42 rotates the first ratchet 50 by engaging the idler gear 70.
When the second bi-directional driving motor 30 moves the shutter-driving ring 44 toward a positive direction to a predetermined position, which is an appropriate position for focusing, the first bi-directional driving motor 20 controls the electromagnetic valve 22 to stop rotating the first ratchet 50. At this time, a pull-back action to the retaining member 42, which is generated by the elastic element 34, is stopped due to the stop action of the electromagnetic valve 22. Thus, the lens barrel 18 and the shutter-driving ring 44 do not circumrotate so that the lens driving device 10 can focus and retain position. At this time, the shutter-driving ring 44 moves to a predetermined shutter position and opens the shutter, and the lens barrel 18 also drives the focusing lens 14 to rotate to a corresponding position.
The second bidirectional driving motor 30 continues to rotate in a positive direction and moves the shutter-driving ring 44 to an utmost position 45. At the same time, the first bi-directional driving motor 20 drives the electromagnetic valve 22 to rotate the first ratchet 50 so that the first ratchet 50 and the retaining member 42 rotate to corresponding utmost positions. At this time, the second bi-directional driving motor 30 provides no power to the lens driving device 10. That means after the second bi-directional driving motor 30 moves the shutter-driving ring 44 to utmost position 45, only the first bidirectional driving motor 20 provides a small amount of power to move focus retaining mechanisms such as the first ratchet 50, the retaining member 42, the lens barrel 18, the shutter-driving ring 44, and the elastic element 34 back to an initial state. After the first bi-directional driving motor 20 drives the electromagnetic valve 22 and the first ratchet 50 to their utmost positions, the first ratchet 50 does not contact with the electromagnetic valve 22, and a spring 62 disposed on the base 12 pulls the hold lever 60 back to the initial state. This is an action of closing the shutter. In addition, the elastic element 34 also pulls the retaining member 42 back to the initial state so that the shutter-driving ring 44, lens barrel 18, and the first ratchet 50 are also moved back to the initial states.
As described above, the prior lens driving device 10 has a complicated focus retaining mechanism, and an electromagnetic valve and a gear assembly are needed. Thus, the complexity and costs of components are increased. In addition, although the electromagnetic valve 22 acts effectively, the available space of the lens driving device 10 is decreased with the use of the electromagnetic valve 22.
It is therefore a primary objective of the claimed invention to provide a focus retaining mechanism of a camera with a simple design to solve the above-mentioned problem.
The claimed invention provides a focus retaining mechanism of a camera. The camera comprises a base, a focusing lens, a retaining wheel, a pushing member, and a retaining hook. The base has a cylindrical and vertical opening in it. The focusing lens is rotationally fixed within the opening. The retaining wheel is rotationally fixed in the base. The horizontal sides of the retaining wheel include a ratchet side, a smooth side, a first end, and a second end positioned over the connecting portions of the ratchet side and the smooth side. The pushing member is horizontally and movably fixed in the base for moving the focusing lens and the retaining wheel. The retaining hook includes a horizontal arm and a vertical arm. The horizontal arm can move across the upper side of the retaining wheel, and the vertical arm can thus contact each of the horizontal sides of the retaining wheel.
It is an advantage of the claimed invention that a focus retaining mechanism of a camera with a simple design is used for simplifying the focus retaining mechanism. These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment, which is illustrated in the various figures and drawings.